With the recent development of digital technologies, various types of electronic devices such as mobile communication terminals, smart phones, tablet Personal Computers (PC), Personal Digital Assistants (PDA), electronic notes, notebooks, wearable devices, and televisions (TV) are widely used. In such electronic devices, a display area is not only on the front surface of an electronic device but also extends to the right and left side surfaces of the electronic device. For example, when a bent display is applied to an electronic device, the right and left edge parts of the display may be bent to make a screen look larger.